1. Technical Field
The present disclosure relates generally to an apparatus for remotely actuating an end effector disposed at a distal end of a surgical instrument. In particular, the apparatus transmits a rotational movement through a shaft of the instrument to maintain a position of the end effector throughout actuation of the end effector.
2. Background of Related Art
Typically in a laparoscopic, an endoscopic, or other minimally invasive surgical procedure, a small incision or puncture is made in a patient's body. A cannula is then inserted into a body cavity through the incision, which provides a passageway for inserting various surgical devices such as scissors, dissectors, retractors, or similar instruments. To facilitate operability through the cannula, instruments adapted for laparoscopic surgery typically include a relatively narrow shaft supporting an end effector at its distal end and a handle at its proximal end. Arranging the shaft of such an instrument through the cannula allows a surgeon to manipulate the proximal handle from outside the body to cause the distal end effector to carry out a surgical procedure at a remote internal surgical site. This type of laparoscopic procedure has proven beneficial over traditional open surgery due to reduced trauma, improved healing and other attendant advantages.
An articulating laparoscopic or endoscopic instrument may provide a surgeon with a range of operability suitable for a particular surgical procedure. The instrument may be configured such that the end effector may be aligned with an axis of the instrument to facilitate insertion through a cannula, and thereafter, the end effector may be selectively articulated, pivoted or moved off-axis as necessary to appropriately engage tissue. When the end effector of an articulating instrument includes a pair of jaw members for grasping tissue, a force transmission mechanism such as a flexible control wire may be provided to open or close the jaws. For example, the control wire may extend through an outer shaft from the handle to the jaws such that the surgeon may create a tension in the control wire to cause the jaws to move closer to one another. The closure or clamping force generated in the jaws may be directly related to the tension in the control wire applied by the surgeon.
One type of laparoscopic or endoscopic instrument is intended to generate a significant closure force between jaw members to seal small diameter blood vessels, vascular bundles or any two layers of tissue with the application electrosurgical or RF energy. The two layers may be grasped and clamped together by the jaws of an electrosurgical forceps, and an appropriate amount of electrosurgical energy may be applied through the jaws. In this way, the two layers of tissue may be fused together. The closure forces typically generated by this type of procedure may present difficulties when using a typical control wire to open and close the jaws of an articulating instrument.
For example, a surgeon's efforts to position the jaws may be frustrated by a tendency for a control wire under tension to realign the jaws with the axis of the instrument after the jaws have been articulated off-axis. Although this tendency may be observed in any type of articulating instrument, the tendency is particularly apparent when the closure forces and necessary tension in the control wire are relatively high, as is common in an electrosurgical sealing instrument. This tendency may be created by the direction of reaction forces through the outer shaft of the instrument.